TORNADOSBY: BRANDI THORPE

WHAT IS A TORNADO?

• tor·na·do

• [tôrˈnādō]

• NOUN

• a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.

• synonyms: windstorm · tempest · whirlwind · gale · strong wind

• A tornado is a violently rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as twisters or cyclones, although the word cyclone is used in meteorology, in a wider sense, to name any closed low pressure circulation.

• A tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes are the most violent of all atmospheric storms.

WHAT CAUSES A TORNADO?• Tornadoes form in unusually violent thunderstorms when there is sufficient (1) instability and (2) wind shear present in the lower atmosphere.

• Instability refers to unusually warm and humid conditions in the lower atmosphere, and possibly cooler than usual conditions in the upper atmosphere. Wind shear in this case refers to the wind direction changing, and the wind speed increasing, with height. An example would be a southerly wind of 15 mph at the surface, changing to a southwesterly or westerly wind of 50 mph at 5,000 feet altitude.

• This kind of wind shear and instability usually exists only ahead of a cold front and low pressure system. The intense spinning of a tornado is partly the result of the updrafts and downdrafts in the thunderstorm (caused by the unstable air) interacting with the wind shear, resulting in a tilting of the wind shear to form an upright tornado vortex. Helping the process along, cyclonically flowing air around the cyclone, already slowly spinning in a counter-clockwise direction (in the Northern Hemisphere), converges inward toward the thunderstorm, causing it to spin faster. This is the same process that causes an ice skater to spin faster when she pulls her arms in toward her body.

• Other processes can enhance the chances for tornado formation. For instance, dry air in the middle atmosphere can be rapidly cooled by rain in the thunderstorm, strengthening the downdrafts that assist in tornado formation. Notice that in virtually every picture you see of a tornado the tornado has formed on the boundary between dark clouds (the storm updraft region) and bright clouds (the storm downdraft region), evidence of the importance of updrafts and downdrafts to tornado formation.

• Also, an isolated strong thunderstorm just ahead of a squall line that then merges with the squall line often becomes tornadic; isolated storms are more likely to form tornadoes than squall lines, since an isolated storm can form a more symmetric flow pattern around it, and the isolated storm also has less competition for the unstable air which fuels the storm than if it were part of a solid line (squall line) of storms.

• Because both instability and wind shear are necessary for tornado formation, sometimes weak tornadoes can occur when the wind shear conditions are strong, but the atmosphere is not very unstable. For instance, this sometimes happens in California in the winter when a strong low pressure system comes ashore. Similarly, weak tornadoes can occur when the air mass is very unstable, but has little wind shear. For instance, Florida -- which reports more tornadoes than any other state in the U.S. -- has many weaker tornadoes of this variety. Of course, the most violent tornadoes occur when both strong instability and strong wind shear are present, which in the U.S. occurs in the middle part of the country during the spring, and to a lesser extent during fall.

WHAT PREDICTION TOOLS CAN BE USED TO PREDICT TORNADOS?

• Barometer

• Thermometer

• Anemometer

• Weather radar

• Doppler

• A barometer measures atmospheric pressure, a thermometer measures the temperature, and an anemometer measures wind speed and direction. Weather radar detects precipitation in the clouds, and the Doppler radar takes measurements of winds in clouds in order to predict severe storms and tornadoes.

WHAT ARE THE EFFECTS OF A TORNADO?

• Impact of tornadoes. Like all natural disasters such as hurricanes, earthquakes, floods and others, they end up with massive destruction to homes, property, infrastructure and cause many deaths as well. Each year, about 60 people are killed by tornadoes, mostly from airborne debris.

WHERE DO TORNADOS MOSTLY OCCUR?

• More than 500 tornadoes typically occur in this area every year and is why it is commonly known as "Tornado Alley". Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, Iowa, Missouri, Arkansas and Louisiana all make up Tornado Alley.

HOW CAN A PERSON PREPARE OR AVOID A TORNADO?

• Discuss a plan and practice it.[2] Create a list with contact information, insurance information, and in case of emergency out of town contacts. Make sure everyone in the family knows where to go, what to take, and how to be safe if a tornado hits.

• Create an emergency kit.[4] This should include water and food for at least 72 hours. Having a means of communication or information (radio, satellite phone, etc.) is also important to include. Any first aid supplies, clothes, and toiletries that you may need should be stored along with flashlights, batteries, etc.

HOW IS THE STRENGTH OR IMPACT OF A TORNADO MEASURED?

• The EF Scale (below) is the standard way to measure tornadoes based on wind damage. The original Fujita Scale (or F Scale) was developed by Dr. Theodore Fujita. All tornadoes, and other severe local windstorms, were assigned a number according to the most intense damage caused by the storm.

SOURCES:

Slide 2: www.nssl.noaa.gov/education/svrwx101/tornadoes/

https://en.wikipedia.org/wiki/Tornado

Slide 3: http://www.weatherquestions.com/What_causes_tornadoes.htm

Slide 4: http://www.weatherwizkids.com/weather-tornado.htm

Slide 5: http://eschooltoday.com/natural-disasters/tornadoes/impact-of-tornadoes.html

Slide 6: www.weatherwizkids.com/weather-tornado.htm

Slide 7: http://www.wikihow.com/Prepare-For-a-Tornado

Slide 8: www.almanac.com/content/how-measure-tornadoes-ef-scale

REAL TORNADOS

https://www.youtube.com/watch?v=8Xftgtl4PlM

https://www.youtube.com/watch?v=DXqUJpJn2_s

THX FOR WATCHING!